| Rosin modified phenolic resin is widely used in offset printing ink, which acts an important role in determining the quality of resin. It is now clear that printing ink has a complex rheological behavior for it is a typical decentralized system, and as a core component of printing ink, the vehicle determines the rheological characteristics of the system. Therefore, to syntheze a high performance of rosin-modified phenolic resin and to study the rheology of its vehicles is considerable for development of the green printing ink.In this paper, the effect of different formulation and technical process on the performance of rosin-modified phenolic resin was studied. The resin was synthesized by one-step process employing rosin, fumaric acid (FA), alkyl-hydroxybenzene, polyphosphate formaldehyde and pentaerythritol as raw materials. Four alkyl-phenol monomers including dodecylphenol (DP), nonyl phenol (NP),4-tert-octylphenol (OP) and4-tert-butylphenol (BP) were used to synthesis four different properties of resins, which were noted as RDP, RNP, ROP and RBP respectively. The influence of the properties of the alkyl-phenol on the structure and properties of rosin-modified phenolic resins were characterized by viscosity solubility testing, FT-IR, DSC-TG, GPC and Rheology respectively. It is clear that RDP and ROP are both have a high molecular weight. Unfortunately, the former gives a low viscosity and the later shows poor solubility. Accordingly, a mixture of DP and OP was employed to prepare rosin-modefied mix-alkylphenolic resin. The formulation and technical process was also optimized and the alternative modified resin was obtained with a high viscosity of22～24Pa·s/25℃, high softening point of168～170℃, and high n-heptane values of6-8mL/2g. It can be applied on manufacturing high-grade offset printing ink.Moreover, the resultant resin was combined with linseed oil, high boiling points kerosene and JP gelling agent (made in Japan) to prepare a gel-type vehicle for printing ink. The effects of amounts of linseed oil, high boiling points kerosene and gelling agent on the rheological property of vehicles were investigated. Based on the experimental results, the viscosity models was setup to accurately describe the viscosity of the gel-type vehicles at various raw material ratios, temperatures and shear speeds. Software for formula calculation was design using the assembler language, which can adjust the rheological parameters according to changes of the main factors to optimize formula for vehicle with constant quality rapidly.Finally, the effects of various formulation and process on the rheological properties of vehicles were studied using rheologic methods. Compared with holding temperature and holding time, the amount of JP gelata plays more important role on the rheological properties of vehicles. It is shown that a strong sol system with optimum viscosity and flow activation energy can obtained at0.8wt.%gelling agent. The effect of vehicle’s viscosity and flow activation energy at holding temperature of170～185℃is equivalent with that of at holding time of30～45min. This is an essential for improving the preparation technical process of gel-type vehicle. Accordingly, in this study, holding temperature and time were selected to be of185℃and35min respectively. And the effects of various gelatas (JP, CN-1, CN-2, CN-3) on the rheological properties of vehicles were then studied. The results show that the dosage is the dominant parameter for three domestic gelatas (CN-1, CN-2, CN-3). Moreover, at same formula and process vehicles prepared from CN-1and from JP give a similar viscoelastic, suggesting that CN-1gelata can partly replace JP gelata. However, JP results in better dispersion, wettability and thermalstability due to its good gelling effect. The vehicle obtained from JP can be applied on producing high-grade printing inks. |
PDF Full Text Request